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........ published in NEWSLETTER # 65

ELECTRON CRYSTALLOGRAPHY
By Dr. D.L. Dorset, Hautpman-Woodward Institute, Buffalo/NY (U.S.A.)

The NATO Advanced Study Institute on "Electron Crystallography" held in June 1997 at the Ettore Majorana Centre in Erice, Italy, was organized by S. Hovmoller, X.D. Zou and D.L. Dorset. The ASI volume (NATO ASI SERIES E347) was published by Kluwer in December 1997. This ASI was the successor to the NATO ASW on "Electron Crystallography or Organic Moluecules" held at the same site in April 1990, organized by J.R. Fryer and D.L. Dorset, the resulting volume C 328 also published in 1991 by Kluwer. Significant progress in this emergent crystallographic technique has taken place within the decade to warrant the most recent Advanced Study Institute which was very successful and well-attended. The Institute was enriched by the concurrent ASI on "Direct Methods of Solving Macromolecular Structure", organized by S. Fortier and H. Schenk in that some lectures presented topics of interest to both schools in a few joint sessions (see volume C507).

This ASI volume provides a current overview of how electron diffraction and microscopic data can be used for the quantitative determination of crystal structures. Theoretical papers discuss the multiple beam scattering of electrons scattered by thin crystals and how experimental conditions can be established, either to utilize these interactions producitvely for symmetry or crystallographic phase determination or to minimize their effect in data collection to permit structure analyses by more traditional, 'quasi-kinemtatical', approaches. Crystallographic phase determination by direct methods, either by ab initio probabilistic or algebraic methods, or by image analysis, or by a combination of both methods, is described for many applications. Refinement methods are also surveyed, including Fourier techniques or least squares methods, addressing problems imposed by multiple scattering perturbations. One refinement method, however, actually exploits the dynamical scattering signal. Applications areas include the structure determination of numerous inorganic structures (alloys, metal oxides, high Tc superconductors, minerals, etc.), organics (synthetic polymers, pigments, nonlinear optical materials, etc.), as well as globular macromolecules, including integral membrane proteins. Methods for specimen preparation are also discussed.
Reference books: A126, B247, C221, C328, C480, C507, E263, E347

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